Alleles

• What are dominant and recessive alleles?

  Dominant alleles are expressed in the phenotype even if only one copy is present, while recessive alleles are expressed only if two copies are present.
• What is the definition of homozygous and heterozygous?

  • Homozygous: having two identical alleles for a trait
  • Heterozygous: having two different alleles for a trait
• What is the difference between genotype and phenotype?

  Genotype refers to the alleles present, while phenotype refers to the characteristics caused by those alleles.
• Why is it important to learn definitions related to genetics?

  Because they are fundamental to understanding genetics and inheritance.
• How many pairs of chromosomes do normal human cells contain?

  Normal human cells contain 23 pairs of chromosomes.
• From whom do humans inherit their chromosomes?

  From their father and mother.
• What are genes?

  Genes are sections of DNA on a chromosome.
• What is the significance of alleles in genetics?

  They are versions of a gene that determine different traits.
• What does the genotype of a person indicate?

  The genotype indicates the alleles present in an individual.
• What is the relationship between genotype and phenotype?

  • Genotype determines the alleles present
  • Phenotype is the observable characteristic resulting from the genotype
• What is the phenotype of a person with two alleles for dry earwax?

  The phenotype is dry earwax.
• What is the genotype of a person with two alleles for wet earwax?

  The genotype is capital E capital E.
• How does the presence of dominant and recessive alleles affect phenotype?

  A dominant allele will show in the phenotype, while a recessive allele requires two copies to show.
• What are the characteristics of dominant and recessive alleles?

  • Dominant alleles: expressed with one copy, mask recessive alleles
  • Recessive alleles: expressed only when two copies are present
• What is the phenotype of a person who is heterozygous for earwax alleles?

  The phenotype is wet earwax.
• What is the significance of the allele for wet earwax being dominant?

  • It determines the phenotype when present
  • It masks the effect of the recessive allele for dry earwax
• What is the difference between single-gene traits and polygenic traits?

  • Single-gene traits: controlled by one gene
  • Polygenic traits: influenced by multiple genes acting together